Convergence system for a color picture tube



"March 10, 1970 MASAHIDE SAWAl 3,599,114

CONVERGENCE SYSTEM FOR A COLOR PICTURE TUBE Filed Aug. 19, 1968 2 SheetsSheet 1 INVENTOR. 444.5'4/7/05 SAW/U AVTUR/VEY- March 10, 1970 MASAHIDE SAWAI CONVERGENCE SYSTEM FOR A COLOR PICTURE TUBE Filed Aug. 19, 1968 2 Sheets-Sheet 2 g INVENTOR.

MAS/JH/DE SAW/ll.

BYY

3,500,114 CONVERGENCE SYSTEM FOR A COLGR PICTURE TUBE Masahide Sawai, Tokyo, Japan, assignor to Sony Corporation, Tokyo, Japan, a corporation of Japan Fiied Aug. 19, 1968, Ser. No. 753,694 Claims priority, application Japan, Aug. 24, 1967, 42/ 53,984 Int. Cl. H015 29/50 US. Cl. 315-13 6 Claims ABSTRACT OF THE DISCLOSURE In a color picture tube of the single-gun, plural-beam type in which the beams originate in a common horizontal or vertical plane and are passed through the optical center of an electron lens by which they are focussed on the color phosphor screen, and in which two of the beams emerge from the lens along paths that are divergent with respect to the path of a central beam and are to be converged with the latter by passage between convergence deflecting plates having a voltage diflerence applied thereto; the misconvergence of the beams at the beam selecting grid r mask that may result from spherical aberration of the deflection yoke provided for causing the beams to scan the screen is corrected by including in the voltage applied to the convergence deflecting plates a dynamic convergence voltage varied with the sweep signal applied to the yoke for deflecting the beams in the direction of the common plane in which the beams originate to eliminate the component of the misconvergence parallel to such plane, and the component of the misconvergence in the direction at right angles to that plane is eliminated by providing the deflection yoke with a suitable non-uniform magnetic field for deflecting the beams in the last mentioned direction.

This invention relates generally to color picture tubes of the single-gun, plural-beam type, and particularly to tubes of that type in which the plural beams are passed through the optical center of a common electron lens by which the beams are focussed on the color phosphor screen.

In single-gun, plural-beam color picture tubes of the described type, for example, as specifically disclosed in the copending US. application Ser. No. 697,414, filed Jan. 12, 1968, now Patent No. 3,448,316, and having a common assignee herewith, three laterally spaced electron beams are emitted or originated by a beam generating or cathode assembly and directed in a common substantially horizontal or vertical plane with the central beam coinciding with the optical axis of the single electron lens and the two outer beams being converged to cross the central beam at the optical center of the lens and thus emerge from the latter along paths that are divergent from the optical axis. Arranged along such divergent paths are pairs of convergence deflecting plates having voltages applied thereacross to deflect the divergent beams substantially in the plane of origination thereof for causing all beams to converge at a point on the apertured beam selecting grid or shadow mask associated with the color screen. After passing between the convergence deflecting plates, the beams are acted upon by the magnetic fields resulting from the application of horizontal and vertical sweep signals to the corresponding coils of a deflection yoke, whereby the beams are made to scan the screen in the desired raster. It will be apparent that, when the three beams are deflected by the yoke from a point of convergence at the center of the screen, as during scanning, the distances that such beams travel through the magnetic fields of the deflection yoke are relatively varied and 3,5liil,ll4 Patented Mar. 10, 1970 spherical aberration results, that is, the beams undergo diflerent degrees of deflection resulting in misconvergence of the beams, particularly when the latter are directed at corner portions of the screen.

It is an object of this invention to avoid the above mentioned misconvergence of the beams in color picture tubes of the described type.

More specifically, it is an object of this invention to correct or avoid the misconvergence of the beams in a color picture tube of the described type that results from the magnetic fields of the deflection yoke.

According to an aspect of this invention, a single-gun, plural-beam color picture tube as described has applied to its convergence deflecting plates a static convergence voltage and also a dynamic convergence voltage which is varied in synchronism with the sweep signal applied to the yoke for deflecting the beams in the direction of the plane in which the beams originate whereby to eliminate the component of the misconvergence parallel to such plane, and the component of misconvergence in the direction at right angles to that plane is eliminated by providing the deflection yoke with a suitably non-uniform magnetic field for deflecting the beams in the last mentioned direction.

In the case where the beams originate or are generated in a common horizontal plane, horizontal dynamic convergence is achieved by supplying to the convergence deflecting plates a dynamic convergence voltage synchronized with the horizontal sweep signal, and the vertical deflection coil means of the deflection yoke is given a configuration to provide a so-called barrel-shaped magnetic field for eliminating the vertical component of misconvergence.

Conversely, when the beams originate or are generated in a common vertical plane, a dynamic convergence voltage synchronized with the vertical sweep signal is applied to the convergence deflecting plates to eliminate the vertical component of misconvergence, and the horizontal deflection coil means of the deflection yoke is given a configuration to provide a so-called pincushion-shaped magnetic field for eliminating the horizontal component of misconvergence.

The above, and other objects, features and advantages of the invention, will be apparent in the following detailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic sectional view in a horizontal lane passing through the axis of a single-gum pluralbeam color picture tube of the type to which this invention is applied;

FIG. 2 is a schematic end elevational view of a deflection yoke according to this invention for use in the color picture tube of FIG. 1;

FIG. 3 is a detail, diagrammatic view illustrating the windings provided in the deflection yoke of FIG. 2;

FIG. 4 is a diagrammatic view showing the pattern of the magnetic lines of flux in the magnetic field produced by the vertical deflection coil in the yoke of FIGS. 2 and 3;

FIG. 5 is a circuit diagram of a suitable convergence voltage generating means that may be used in connec tion with the color picture tube according to this invention;

FIG. 6 is a view similar to that of FIG. 3, but showing the windings provided in the deflection yoke for a color picture tube according to this invention in which the beams originate in a common vertical plane;

FIG. 7 is a view similar to that of FIG. 4, but showing the pattern of the magnetic lines of flux in the magnetic field produced by the horizontal deflection coil in the yoke of FIG. 6; and

FIG. 8 is a diagrammatic view to illustrate the nature of the misconvergence to be corrected or eliminated according to this invention.

Referring to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that a single-gun, pluralbeam color picture tube 10 of the type to which this invention is applied may comprise a glass envelope (not shown) having a neck and a cone extending from the neck to a color screen S provided with the usual arrays of color phospors S S and S and with an apertured beam selecting grid or shadow mask G Disposed within the neck is a single electron gun having cathodes K K and K each of which is constituted by a beam-generating source with the respective beam-generating surfaces thereof disposed as shown in a plane which is substantially perpendicular to the axis of the electron gun. In the embodiment shown, the beam-generating surfaces are arranged in a straight line so that the respective beams B 13 and B emitted therefrom are directed in a substantially horizontal plane containing the axis of the gun, with the central beam B being coincident with such axis. A first grid G is spaced from the beamgenerating surfaces of cathodes K K and K and has apertures g g and g formed therein in alignment with the respective cathode beam-generating surfaces A common grid G is spaced from the first grid G and has apertures g g and g formed therein in alignment with the respective apertures of the first grid G Successively arranged in the axial direction away from the common grid G are open-ended, tubular grids or electrodes G G and G respectively, with cathodes K K and K grids G and G and electrodes G G and G being maintained in the depicted assembled positions thereof, by suitable, non-illustrated support means of an insulating material.

For operation of the electron gun of FIG. 1, appropriate voltages are applied to the grids G and G and to the electrodes G G and G Thus, for example, a voltage of O to minus 400 v. is applied to the grid G a voltage of 0 to 500 v. is applied to the grid G a voltage of 13 to kv. is applied to the electrodes G and G and a voltage of 0 to 400 v. is applied to the electrode G with all of these voltages being based upon the cathode voltage as a reference. As a result, the voltage distributions between the respective electrodes and cathodes, and the respective lengths and diameters thereof, may be Substantially identical with those of a unipotential-single beam type electron gun which is constituted by a single cathode and first and second, single-apertured grids,

With the applied voltage distribution as described hereinabove, an electron lens field will be established between grid G and the electrode G to form an auxiliary lens L as indicated in dashed lines, and an electron lens field will be established around the axis of the electrode G by the electrodes G G and G to form a main lens L,

again as indicated in dashed lines. In a typical use of electron gun A, bias voltages of 100 v., 0 v., 300 v., 20 kv., 200 v. and 20 v. may be applied respectively to the cathodes K K and K the first and second grids G and G and the electrodes G G and G Further included in the electron gun of FIG. 1 are electron beam convergence deflecting means P which comprise shielding plates P and P disposed in the depicted spaced, relationship at opposite sides of the gun axis, and axially extending, deflector plates Q and Q which are disposed, as shown, in outwardly spaced, opposed relationship to shielding plates P and P, respectively. Although depicted as substantially straight, it is to be understood that the deflector plates Q and Q may, alternatively, be somewhat curved or outwardly bowed, as is well known in the art.

The shielding plates P and P are equally charged and disposed so that the central electron beam B will pass substantially undeflected between the shielding plates P and P, while the deflector plates Q and Q have negative charges with respect to the plates P and P so that respective electron beams B and B will be convergently deflected as shown by the respective passages thereof between the plates P and Q and the plates P and Q. More specifically, a voltage V which is equal to the voltage applied to the electrode G may be applied to both shielding plates P and P, and a voltage V which is some 200 to 300 v. lower than the voltage V is applied to the respective deflector plates Q and Q to result in the respective shielding plates P and P being at the same potential, and to result in the application of a deflecting voltage difference or convergence deflecting voltages between the respective plates P and Q and P and Q and it is, of course, this convergence deflecting voltage V which will impart the requisite convergent deflection to the respective electron beams BB and BR,

In operation, the respective electron beams B B and B which emanate from the beam generating surfaces of the cathodes K K and K will pass through the respective grid apertures g g and g to be intensity modulated with what may be termed the red, green and blue intensity modulation signals applied between the said cathodes and the first grid G The respective electron beams will then pass through the common auxiliary lens L to cross each other at the center of the main lens L and to emerge from the latter with beams B and B diverging from beam B Thereafter, the central electron beam B will pass substantially undeflected between shielding plates P and P since the latter are at the same potential. Passage of the electron beam B between the plates P and Q and of the electron beam B between the plates P and Q will however, result in the convergent deflections thereof as a result of the convergence deflecting voltage applied therebetween, and the system of FIG. 1 is so arranged that the electron beams B B and B will desirably converge or cross each other at a common spot centered in an aperture between adjacent grid wires g of the beam selecting grid or mask G so as to diverge therefrom to strike the respective color phosphors of a corresponding array thereof on screen S. More specifically, it may be noted that the color phosphor screen S is composed of a large plurality of sets or arrays of vertically extending red, green and blue phosphor stripes or dots S S and S with each of the arrays or sets of color phosphors forming a color picture element as in a chromatron type color picture tube. Thus, it will be understood that the common spot of beam convergence corresponds to one of the thusly formed color picture elements.

The voltage V may also be applied to the lens electrodes G and G and to the screen S as an anode voltage in conventional manner through a non-illustrated graphite layer which is provided on the inner surface of cone 13 of the tube envelope. The grid wires of screen grid G may have a post-focussing voltage ranging, for example, from 6 to 7 kv. applied thereto. Thus, to summarize the operation of the depicted color picture tube of FIG. 1, the respective electron beam B B and B will be converged at screen grid G and will diverge therefrom in such manner that electron beam B will strike the blue phosphor S electron beam B .will strike the green phosphor S and electron beam B will strike the red phosphor S of the array or set corresponding to the grid aperture at which the beams converge. Electron beam scanning of the face of the color phosphor screen is eflected by horizontal and vertical deflection yoke means indicated in broken lines at 20 and which receives horizontal and vertical sweep signals whereby a color picture will be provided on the color screen. Since, with this arrangement, the respective electron beams are each passed, for focussing, through the center of the main lens L of the electron gun A, the beam spot formed by impingement of the beams on the color phosphor screen S will be substantially free from the effects of coma and/ or astigmatism of the said main lens, whereby improved color picture resolution will be provided.

It will be apparent that, when beams B B and B are deflected by yoke means from a point of convergence at the center of grid G and screen S, as during scanning of the screen, the distances that such beams travel through the magnetic fields of yoke means 20 are relatively varied and, is such fields are uniform or have uniformly spaced lines of flux, spherical aberration results, that is, the beams undergo different degrees of deflection resulting in misconvergence of the beams, particularly when the latter are directed at corner portions of the screen, as shown in FIG. 8. Such misconvergence of the beams has a vertical component and a horizontal Component by reason of the magnetic fields produced by yoke means 20 for deflecting the beams in vertical and horizontal directions.

In the color picture tube according to this invention the horizontal component of the described misconvergence, that is, the component in the direction of the common plane in which the beams are generated and hence in the direction that the beams B and B are deflected by convergence deflecting means F, is compensated for by means which apply across plates P and Q and plates P and Q in addition to a static convergence deflection voltage, a dynamic convergence deflection voltage synchronized with the horizontal sweep signal so as to suitably vary the deflections of beams B and B by convergence deflections means F for compensating or eliminating the horizontal component of misconvergence. A circuit for generating the dynamic convergence deflecting voltage in addition to the static convergence deflecting voltage may be of the kind disclosed in detail in copending US. application Ser. No. 739,383, filed June 24, 1968, now Patent No. 3,452,240, and having a common assignee herewith.

As shown on FIG. 5, such a convergence deflecting voltage generating circuit is connected to therminals t and 1, to apply the requisite voltages to plates P and P and to plates Q and Q, respectively, and is also connected to a fly-back transformer 21 which is in turn connected to a conventional horizontal deflection voltage output circuit (not shown). The fly-back transformer 21 (the primary winding of which is not shown) comprises a closed magnetic core 21a and a high voltage secondary winding 22a. Also wound on the magnetic core 21a is a convergence deflecting voltage secondary winding 22]). The primary winding 23a of an isolating transformer 23 is connected to the winding 22b through a convergence adjusting circuit 25 which may comprise a variable impedance element such as a variable resistor, variable inductance, or the like. Series-connected diode and resistors 29 and 32 of the convergence deflecting voltage generating circuit 24 are connected as indicated across the secondary winding 23b of transformer 23, with the diode 30 being connected in what will later be understood to be the forward direction. In addition, seriesconnected capacitors 31 and 28 are connected in parallel with the resistor 32, and an inductor 27 is connected as shown between the junction of secondary winding 23b and resistor 29, and the connection point of the respective capacitors 31 and 28. Circuit terminals 33a and 33b are connected across the resistor 32.

In operation, a pulse voltage of the horizontal deflection frequency is induced across winding 22b, and imparted to transformer 23 through the adjusting circuit 25. Thus, pulses of the horizontal deflection or sweep frequency occur at secondary winding 23b of transformer 23. Such pulses developed in winding 23b are rectified by the rectifier circuit formed by diode 30, resistors 29 and 32, and capacitors 31 and 28, to provide a static convergence deflecting voltage V across resistor 32 and thus between the output terminals 33a and 33b (terminal 33a being at the higher potential).

In addition, the pulses developed across winding 23b are converted into a voltage of parabolic wave form by means of inductor 27 and capacitor 28 which, as utilized therein, will function in the nature of a double-integrating circuit 26. This voltage of parabolic wave form is a horizontal dynamic convergence voltage E which is also available, through capacitor 31, between the respective circuit terminals 33a and 33b. As a result, the respective static and dynamic convergence voltages V and E are superimposed upon each other to result in a net output voltage (V -i-E between circuit terminals 33a and 33b. The function of the dynamic convergence voltage E is to vary the degree of convergence imposed upon beams B and B according to the differing requirements of the periodically varying horizontal deflection conditions as the three beams are swept horizontally in the usual manner. Deriving the voltage E from fiy-back transformer 21 insures synchronism between E and the horizontal sweep.

Referring again to fly-back transformer 21 it may be noted that high voltage secondary winding 22a thereof is coupled to the anode of a high voltage rectifier circuit 34, the output side 34a of which is connected to terminal 33b of circuit 24 to apply the high output voltage V of rectifier 34 to terminal 33b. The terminal t provided for the spaced, deflecting plates Q and Q is connected as shown to the terminal 33b to receive the high voltage V The terminal t commonly referred to as the anode button, is tied to each of the electrodes G and G and shielding plates P and P, and is connected as shown to terminal 33a of circuit 24. The terminal I is also connected to the graphite coating on the cathode ray tube cone portion, mentioned previously. As a result, the voltage appearing at the terminal t will be applied to each of electrodes G and G shielding plates P and P, and as an anode voltage to the color phosphor screen S.

With the convergence voltage generating circuit 24 described, the voltage V appearing at the output side of rectifier circuit34, and thus at terminal t is applied to the deflecting plates Q and Q. The anode voltage V which is equal to V -I-(V -i-E will appear at circuit terminal 33a, and thus terminal 1 and will be applied to electrodes G and G shielding plates P and P, and the color phosphor screen S. As a result, the convergence deflection voltage, which is equal to (V -l-E is applied between the plates P and Q and between the plates P and Q, the potential at the outer plates Q and Q being negative with respect to that at the inner plates P and P. The magnitude of the static convergence voltage V and the amplitude of the dynamic convergence voltage E may be adjusted by means of circuit 25. In practice, the magnitude of voltage V is adjusted within a ran e of 200 to 350 v., and the amplitude of voltage E within a range of 30 to 60 v. By means of the circuit described, the adjusted static convergence voltage V is applied to the convergence means F of the illustrated single-gun, three-beam type color picture tube so as to provide for proper convergence of the respective electron beams B B and B at a common spot at the center of the screen grid G which results in proper aiming of the beams toward the respective color phosphor stripes S S and S In addition, the adjusted horizontal dynamic convergence deflecting voltage E will be simultaneously applied to the deflecting means P so that as the beams are deflected from the central position, the effect of such dynamic convergence deflecting voltage will be to compensate for or eliminate substantially the horizontal component of the misconvergence illustrated on FIG. 8 and which results from the effect of the magnetic field of the horizontal deflecting yoke of yoke means 20.

In accordance with this invention the vertical component of the misconvergence shown on FIG. 8 is elimi nated, that, is vertical dynamic convergence is etfected, by providing the vertical deflecting yoke of yoke means with a configuration that results in a non-uniform field, more particularly a so-called "barrel-shaped field, when the vertical swee signal is applied thereto.

As shown on Fig. 2, the deflecting yoke means 20 according to this invention comprises a vertical deflecting yoke constituted by separately wound upper vertical deflection coils a and 35b arranged on an annular or doughnut-shaped magnetic core 36 and by separately wound lower vertical deflection coils 37a and 3712 also arranged on core 36. As shown, the coils 35a and 37a are respectively arranged above and below the horizontal plane YY which extends through the center of core 36 at one side of the vertical plane XX extending through such center, and coils 35b and 37b are similarly arranged above and below plane YY at the opposite side of plane XX,

The coils 35a and 3517 are Wound in the same direction with a gap 38 therebetween and coils 37a and 371) have a similar gap 38 therebetween and, as shown on FIGS. 3, are wound in the same direction which is opposed to the direction of winding of coils 35a and 35b. Further, the coils 35a and 35b and the oppositely wound coils 37a and 37b are connected in series, as shown, to terminals 39a and 3%, as shown on FIG. 3, to which there is applied the vertical sweep signal for providing, by the resulting current flows through the series connected coils, the desired barrel-shaped magnetic field M (FIG. 4).

The angular extents Q, of coils 35a and 35b and of coils 37a and 37b, and the size of the gaps 38 determine the shape of field M and such dimensions are selected so that the resulting barrel-shape of the field will atford vertical dynamic convergence, that is, will compensate for or eliminate the vertical component of misconvergence that would result from the passage of beams B B and B through the magnetic field of the vertical deflection yoke if such field was uniform.

As shown on FIGS. 2 and 3, the yoke means 20 according to this invention may further comprise the usual horizontal deflection yoke constituted by coils 40a and 4012 which are oppositely wound and connected in series to terminals 41a and 41b which receives the horizontal sweep signal, As previousl described, in this embodiment of the invention, the horizontal component of misconvergence that results from passage of the beams through the magnetic field established by coils 40a and 40b of the horizontal deflection yoke is compensated for, or eliminated by the application to convergence deflecting means F of the horizontal dynamic convergence deflecting voltage E Thus, proper convergence of beams B B and B is maintained at all portions of screen grid G to provide a substantially distortion-free color picture which is virtually free of misconvergence.

If the beams B B and B originates in a common vertical plane, rather than in a common horizontal plane as in the embodiment of FIG. 1, in which case the electron beam convergence deflecting means corresponding to the means F are effective to convergently deflect the beams B and B in a vertical plane to converge with beam B at a common spot on the screen grid or mask, the vertical component of misconvergence that results from passage of the beams through the magnetic field of the vertical deflection yoke is eliminated by applying a vertical dynamic convergence deflecting voltage across the plates of the convergence deflecting means in synchronism with the vertical sweep signal, for example, as by a circuit similar to that of FIG. 5, and the horizontal component of the misconvergence is eliminated, that is, horizontal dynamic convergence is effected, by providing the horizontal deflecting yoke with a configuration that results in a non-uniform magnetic field, more particularly in a co-called pincushion shaped field, when the horizontal sweep signal is applied thereto.

As shown on FIG. 6, the horizontal deflecting yoke of yoke means 20' according to this invention for a color picture tube in which the beams originate in a common vertical plane may be constituted by oppositely wound coils 40'0 and 40'!) on diametrically opposed portions of an annular magnetic core 36, with such oppositely wound horizontal deflecting coils being connected in series to terminals 41a and 4111 which receive the horizontal sweep signal. The lengths d of coils 40'a and 40b are sufficiently limited so that the magnetic field M produced by the current flows therethrough in response to the horizontal sweep signal is of a suitable pin-cushion shape, as shown on FIG. 7, to eliminate the horizontal component of misconvergence.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

What is claimed is:

1. A single-gun, plural-beam color picture tube comprising a color screen having arrays of color phosphors and beam selecting means provided with apertures corresponding to said arrays, beam generating means for directing a plurality of electron beams in a common plane to ward said screen for impingement on respective phosphors of each array through the corresponding aperture, lens means for focusing said electron beams on said screen and having an optical center through which said beams are all passed with at least two or said beams emerging from said lens means along paths lying in said plane and which are divergent to the optical axis of the lens means, electron beam convergence deflecting means located between said lens means and said screen and being operative, upon the application of a convergence deflecting voltage thereto, to deflect said beams emerging along said divergent paths for convergence of said beams at an aperture of said beam selecting means, and deflection yoke means having sweep signals applied thereto to deflect said beams in directions respectively parallel, and at right angles to said plane for causing said beams to scan said screen; and in which misconvergence of said beams at said beam selecting means as a result of spherical aberration of said yoke means is corrected by the combination of means generating said convergence defleeting voltage so as to include in the latter a static convergence voltage and a dynamic convergence voltage which is varied in synchronism with said sweep signals applied to said yoke means for deflection of said beams in said direction parallel to said plane, whereby to eliminate the component of said misconvergence in said direction parallel to said plane, and coil means in said deflection yoke means receiving said sweep signals for deflection of the beams in said direction at right angles to said plane and being arranged to provide a resulting magnetic field which is nonuniform so as to eliminate the component of said misconvergence in said direction at right angles to said plane.

2. A color picture tube according to claim 1, in which said common plane of the electron beams is substantially horizontal, and said magnetic field provided by said coil means is barrel-shaped.

3. A color picture tube according to claim 2, in which said deflection yoke means has an annular magnetic core, and said coil means includes a first pair of coils which are wound in the same direction and arranged on said core above a horizontal plane passing through the center of said core and which are spaced apart at opposite sides of a vertical plane passing through said center, and a second pair of coils arranged on said core below said horizontal plane and being spaced apart at opposite sides of said vertical plane, said coils of the second pair being wound in the direction opposed to said direction of winding of said first pair of coils and being connected in series with the latter to receive the vertical sweep signal.

4. A color picture tube according to claim 3, in which the angular extent of each of said first and second pairs of coils on said core is selected to provide the barrelshape of said magnetic field requisite for the elimination of the vertical component of said misconvergence.

5. A color picture tube according to claim 1, in which said common plane of the electron beams is substantially vertical, and said magnetic field provided by said coil means is of pin-cushion shape.

6. A color picture tube according to claim 5, in which said deflection yoke means has an annular magnetic core, and said coil means includes oppositely wound coils arranged on said core at diametrically opposed side portions of the latter, said coils being series connected to receive the horizontal sweep signal and having the height thereof on said core selected to provide the pin-cushion shape of said magnetic field requisite for the elimination of the horizontal component of said miconvergence.

References Cited UNITED STATES PATENTS r RODNEY D. BENNETT, JR., Primary Examiner O MALCOLM F. HUBLER, Assistant Examiner US. Cl. X.R. 314-27; 3352l3 

